Transcript Methylxanthines Lecture Notes Page

Methylxanthines
RC 195
Types of Methylxanthines
• Caffeine
• Theobromine
• Theophylline
– Most common methylxanthine used in
respiratory care
Methylxanthine Effects
• Bronchodilation
• Cerebral stimulation
• Skeletal muscle
stimulation
• Vasodilator
• Cardiac stimulation
• Smooth muscle
relaxation
• Diuresis
Theophylline
Common Brands
• Aminophylline
– IV administration while hospitalized
• Oxtriphylline
– Oral form
– Choledyl, TheoBid, TheoDur
• Combinations (Theophylline and
sympathomimetc)
– Oral preparations: Marax, Tedral, Quibron, Slo-Phylline
Theophylline Duration
• 3-9 ½ hours
• Is deactivated in liver
• Desired effects and side effects are
determined by serum, ie plasma, levels
Signs that indicate need to check
serum Theophylline levels
•
•
•
•
N &V
Thirst
Agitation
Arrhythmias
Factors that decrease
Theophylline clearance
•
•
•
•
•
CHF
Pneumonia
Pulmonary Edema
Hepatic problems
Drugs- eg, Cimetidine, Erythromycin,
Propranolol
These patients are prone to high serum levels and toxicity
Factors that increase
Theophylline clearance
• Cigarette smoking
• Being a pediatric patient
• Acidosis
These patients may need higher doses to achieve therapeutic levels
Routes and Dosages
• IV
– Loading dose is 6 mg/kg over thirty minutes
(why?) or 3 mg/kg in a patient who has
received Theophylline within last 24 hours
– Maintenance dose:
• .9 mg/kg/hour for person who smokes
• .5 mg/kg/hour for non-smoker
• .25 mg/kg/hour in a patient with decreased clearance
Routes and Dosages (cont.)
• Oral – 100-200 mg TID or QID
– TheoBid and Theodur are BID
• Rectal – 500 mg
• IM – 250-500mg
– Very painful so not a commonly used route
• Theophylline is rarely aerosolized!
– Variable serum levels and intense coughing
Drug Interactions
•
•
•
•
Antagonizes Propranolol
Potentiates sympathomimetics
Additive with diuretics
Antibiotics – variable. May also cause
precipitation if mixed in same IV line
– It is best to administer IV Theophylline in its
own IV line
Time for a case study!